This study is specifically directed at determining in humans, the bioavailability and pharmacokinetics of isoflavones, non-steroidal estrogenic compounds, contained in abundance in soy foods and formulas. The metabolism of these bioactive non-nutrients has been extensively studied in animals, but information in humans is limited. Although we have previously established a level of dietary intake that can invoke a biological response in women, little is known about the bioavailability of isoflavones from different foods or formulas, whether there are large variations among individuals, or gender or age-related differences in absorption or metabolism, and if there are dose-response effects. To this end, we will be determining the bioavailability and pharmacokinetics of soy isoflavones contained in different kinds of foods and formulas.